Fruit production, leaf chlorosis and starch content were examined in cucumber plants under 18 and 24 h (continuous) photoperiods. Light levels were adjusted to provide daily quantum integrals of 16.4 mol m(-2) day(-1) in both treatments. Continuous light reduced fruit production, induced development of chlorosis on young, fully expanded leaves and gave lower starch content, primarily in leaves, compared to 18 h photoperiods. No correlation between chlorosis and hyper-accumulation of starch was found at the onset of visible leaf injury. The present study indicated that a lighting regime with continuous illumination should not be implemented in commercial cucumber production.